1. Technical Field
The present invention relates to an overhead suspension type bonding apparatus in which the bonding head is suspended from an overhead part.
2. Description of the Related Art
An overhead suspension type bonding apparatus has several characterizing features. Namely, since the bonding head is suspended from an overhead part, a workpiece that has a wide bonding area can be bonded. For instance, Japanese Patent Application Laid-Open (Kokai) Nos. 2001-168135 and 2003-297872 disclose bonding apparatuses of this type.
The bonding apparatus of the above-described prior art type has a structure that includes: a bonding arm which has a capillary, a front arm on which the bonding arm is supported by a supporting shaft so that the bonding arm is rotatable and whose upper portion is attached to a bonding head so that the front arm is swingable, a back arm whose front side is supported on the bonding head so that the back arm is rotatable and whose back side is supported on the bonding arm by a connecting shaft so that the back arm is likewise rotatable, and a driving motor that drives the bonding arm. In this structure, the upper surface of the bonding head is fastened to an XY table that is driven in the directions of the X and Y axes, and this XY table is fastened to the overhead part of a bridge stand of the bonding apparatus.
In the above structure, the driving motor is mounted on the bonding arm, and the center of gravity of the movable elements such as the bonding arm and the like is provided above the horizontal plane of the tip end of the capillary. Accordingly, in cases where the XY table is moved at a high speed in the direction of Y axis (i.e., in the axial center direction of the bonding arm), an inertial force acts on the bonding arm which is a movable element, so that a phenomenon occurs in which this bonding arm also moves at the same time, thus forming a bottleneck in the high-speed movement of the bonding head. There is another problem. When the bonding arm is driven by the driving motor, the bonding arm as a whole vibrates by the reaction force of the motor, so that stable bonding cannot be performed.